Order/disorder processes and electromechanical properties of monoclinic GdCa4O(BO3)3
Order/disorder processes and electromechanical properties of monoclinic GdCa4O(BO3)3
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DOI：
10.1515/zkri-2019-0026
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发表时间：
2019-08
期刊：
影响因子：
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通讯作者：
M. Münchhalfen;J. Schreuer;C. Reuther;R. Möckel;J. Götze;E. Mehner;H. Stöcker;D. Meyer
中科院分区：
文献类型：
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作者：
M. Münchhalfen;J. Schreuer;C. Reuther;R. Möckel;J. Götze;E. Mehner;H. Stöcker;D. Meyer
用提拉法生长了GdCa_4 O（BO_3）_3（空间群为Cm）单晶。介电，压电和弹性系数在室温下，以及比热容，热膨胀和阳离子无序采用各种方法，包括共振超声光谱，差示扫描量热法，X-射线衍射技术进行了研究。不同样品上获得的机电参数（4介电，10压电和13弹性刚度系数）是在良好的协议，表明我们的方法的内部一致性高，而文献中报道的值显着不同。GdCa_4 O（BO_3）_3的弹性行为类似于结构相关的氟磷灰石的弹性行为，即弹性各向异性相对较小，并且偏离柯西关系的纵向效应沿阳离子多面体的主导链的方向呈现明显的最小值沿着。GdCa 4 O（BO 3）3的最大纵向压电效应为7.67 × 10−12 CN−10，与硅酸镧镓型材料的压电效应相当。的钙/钆分布的3个独立的阳离子网站的显着变化，伴随着特征异常的热容和热膨胀建议的非收敛的阳离子订购约900 K以上的GdCa 4 O（BO 3）3的过程。
Abstract Large single crystals of GdCa4O(BO3)3 (space group Cm) were grown by the Czochralski method. Dielectric, piezoelectric and elastic coefficients at room temperature as well as specific heat capacity, thermal expansion and cation disorder were studied employing a variety of methods including resonant ultrasound spectroscopy, differential scanning calorimetry, dilatometry and X-ray diffraction techniques. The electromechanical parameters (4 dielectric, 10 piezoelectric and 13 elastic stiffness coefficients) obtained on different samples are in excellent agreement indicating high internal consistency of our approach, whereas the values reported in literature differ significantly. The elastic behaviour of GdCa4O(BO3)3 resembles the one of structurally related fluorapatite, i.e. the elastic anisotropy is relatively small and the longitudinal effect of the deviations from Cauchy-relations exhibit a pronounced minimum along the direction of the dominating chains of cation polyhedra. GdCa4O(BO3)3 exhibits a maximum longitudinal piezoelectric effect of 7.67 × 10−12 CN−10, a value in the order of that of langasite-type materials. Significant changes of the calcium/gadolinium distribution on the 3 independent cation sites accompanied by characteristic anomalies of heat capacity and thermal expansion suggest processes of nonconvergent cation ordering above about 900 K in GdCa4O(BO3)3.